TOPIC CONTAINERS
Volumes & Persistence data that survives restarts
IN 10 SECONDS
Container filesystems are ephemeral. Writable layers are destroyed when a container stops. Volumes mount a directory on the host's physical disk directly into the container filesystem.
GOTCHA Mounting host directories in multi-node clusters fails if pods migrate to different machines. Use cloud block storage (CSI drivers) instead.
HOW DATA PERSISTENCE FLOWS
01 Volume Define user specifies mounting directory path (e.g. /var/lib/mysql) to host path.
02 Mount syscall container runtime intercepts filesystem startup and mounts host directory.
03 Writes application writes database transactions inside mount folder.
04 Recreation container is deleted and recreated; new container mounts same directory, retaining all data.
POKE IT YOURSELF
docker volume ls — list local persistent volumes
docker run -v db_data:/var/lib/mysql mysql — mount volume db_data inside database container
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